1. Field of the Invention
This invention relates generally to devices for improving the performance of internal combusion engines and more particularly to devices for increasing the ratio of air to fuel vapor in the intake manifold of an internal combustion engine at all power settings and engine RPM's above idle.
2. Description of the Prior Art
Various devices have been developed in the past for combusting engine cylinder blow-by, which contains burnt and un-burnt hydrocarbon vapor in order to make a significant reduction in pollutants generated by cars.
Some recent production engines also include an arrangement for recirculating spent exhaust gases (EGR, or Exhaust Gas Recirculation) under controlled conditions. The purpose of EGR is to reduce peak combustion temperatures when each cylinder fires, thus reducing oxygen-nitrogen combinations (NOx) created by engine operation. Introduction of blow-by and exhaust gases in an engine intake system reduces the volume of oxygen available for combustion which in turn increases the percentage of unburnt hydrocarbons and carbon monoxide in the engine exhaust effluent. This places an additional burden on exhaust manifold air injection reactors and exhaust stream catalytic converters, when so used.
All engines will generally exhibit a large or small positive pressure resulting from piston ring blow-by which will increase as the engine shows wear and also as the mean effective compression pressure increases under high power loading. Blow-by gases are composed of unburnt fuel/air mixtures which pass the piston rings during the compression stroke and a mixture of condensed hydrocarbons, CO, CO.sub.2 and water vapor which passes the piston rings during the power stroke. Also included are small quantities of oil residues and particulate matter.
Modern engine designs use so called positive crankcase ventilation (PCV) systems which keep the crankcase under slight negative pressure by drawing filtered external air, usually from the oil filler cap, through the engine crankcase to the pollution control valve on one of the engine valve covers. While recovered blow-by gases are usually too barren to burn alone, injection of blow-by gases into the fuel air mixture will improve gas mileage 3% or more.
Design experience over the past 75 years has demonstrated that it is practically impossible to produce commercial carburation systems which will give a uniform fuel air ratio at all speeds, power settings, temperatures and altitudes, especially during engine throttling. In the interest of ease of starting and smooth operation, the engine designer usually favors a fuel/air mixture which will average out on the rich side (more fuel than actually needed) under all modes of operation.
Thus, a need existed for the development of a reliable air injection system or device operating under control of manifold vacuum to improve overall performance and gas mileage of most cars. This need has long been recognized but never actually satisfied by the development of a relatively simple device to accomplish this goal.
Auxiliary manifold air supply valves for overcoming the shortcomings of the carburetor have been used ever since carburetors first appeared on engines. Manifold air valves have been controlled in a variety of ways, for example: by the throttle linkage; by a Bowden cable linkage adjusted by the driver; by a bi-metallic strip linked to a flapper valve (temperature compensation); by an aneroid capsule linked to an orifice valve (altitude compensation); by a fixed port connected to a partitioned part of the intake manifold (for re-vaporizing condensed fuel when operating temperature is below normal); or as an inverse function of the depression in manifold pressure below atmospheric when the engine is running.
Many current manifold air (MANAIR) systems are controlled by intake manifold vacuum (see, for example U.S. Pat. 3,923,024). Most U.S. type pollution control valves (PCVs) are also actuated by manifold vacuum. A common design consists of a ball check valve spring loaded in the open position. When manifold vacuum drops to the idle or closed throttle valve, the spring resistance is overcome and the ball valve is closed by atmospheric pressure, thus avoiding upset of the engine idle fuel/air ratio. One of the problems of the spring loaded manifold vacuum air admission valve is the wide variation in spring tension requirements for different engine sizes and carburetor configurations. The spring tension can not be easily made adjustable and the ball or modified ball valve is position and shock sensitive. A bad feature of this prior art type ball valve design is that the valve opens and closes within a narrow range of manifold pressures, which leads to mixture problems if the ball check design is used as an air admission valve.
A major objective of this invention is to overcome the above mentioned problems and to provide a simple, reliable, low cost and highly efficient valve device for administering air into internal combusion engines.